doc: add a graphic to explain tap-n-drag

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

1 files changed, 16 insertions, 9 deletions

diff --git a/doc/tapping.dox b/doc/tapping.dox
index 7eb81e6..1337fc5 100644
--- a/doc/tapping.dox
+++ b/doc/tapping.dox
@@ -27,15 +27,22 @@ libinput_device_config_tap_set_enabled() for details.
 
 libinput also supports "tap-and-drag" where a tap immediately followed by a
 finger down and that finger being held down emulates a button press. Moving
-the finger around can thus drag the selected item on the screen. Lifting the
-finger and putting it back down immediately (i.e. within the timeout) will
-continue the dragging process, so that multiple touchpad-widths of distance
-can be covered easily. If two-fingers are supported by the hardware, a
-second finger can be used to drag while the first is held in-place.
-
-An alternative method to end a drag process is to tap immediately after
-lifting the finger. The full sequence is thus: tap, finger down, drag,
-finger up, tap.
+the finger around can thus drag the selected item on the screen.
+
+@image html tap-n-drag.svg "Tap-and-drag process"
+
+The above diagram explains the process, a tap (a) followed by a finger held
+down (b) starts the drag process and logically holds the left mouse button
+down. A movement of the finger (c) will drag the selected item until the
+finger is relased (e). If needed, the finger's position can be reset by
+lifting and quickly setting it down again on the touchpad (d). This will be
+interpreted as continuing move and is especially useful on small touchpads
+or with slow pointer acceleration.
+The release of the mouse buttons after the finger release (e) is triggered
+by a timeout. To release the button immediately, simply tap again (f).
+
+If two fingers are supported by the hardware, a second finger can be used to
+drag while the first is held in-place.
 
 @section tap_constraints Constraints while tapping